Quality Control [2013] Rhydon (QC: 1/2)

Back in Generation 1, Rhydon was one of the best Pokemon around, having a vast movepool and great stats for the time. However, with Rhyperior's introduction in Generation 4, Rhydon seemed to fall into obscurity, now horribly outclassed by this new evolution. Come Generation 5, though, the Eviolite was introduced, and Rhydon gained a new lease on life. When holding an Eviolite, Rhydon becomes ridiculously bulky, even able to survive a Fighting Gem Close Combat from Terrakion, and a lot of other moves that Rhyperior couldn't hope to live. A low base 40 speed might seem unattractive, but the ever-popular Trick Room rids this issue away from Rhydon. Rhydon also has fantastic 130 Attack and can support its allies with Lightningrod. Overall, Rhydon is the much the same as its evolution, except it sets itself apart in various aspects.

Earthquake is the primary STAB for Rhydon, hitting Terrakion, Metagross, and others hard. However, Drill Run can be run over it, in case Rhydon's allies will be affected by Earthquake, and is actually more powerful than a spread Earthquake to one opponent. Rock Slide is another fantastic STAB move, and has a high chance to flinch the opponent, making it a deadly move when Rhydon is under Trick Room. Megahorn hits other common Trick Room Pokemon such as Cresselia, Reuniclus, and Musharna hard, and can keep Ludicolo from OHKOing it. Finally, Protect is a standard move, as Rhydon is weak to a wide variety of types.

[ADDITIONAL COMMENTS]

A 60 HP / 244 Atk / 204 SpD EV spread makes Rhydon more resistant against special attacks, 60 HP allows it to live Fighting Gem Hitmontop's Close Combat, and 204 Sp. D allows it to live Latios' Dragon Gem Draco Meteor. Another EV spread of 252 Atk / 252 Spd / 4 HP allows Rhydon to outspeed Metagross, but also limits its usage in Trick Room. Rhydon's ability Lightningrod acts as fantastic support to its teammates, but be careful, as it can also redirect your partner's Electric-type moves away from the target.

Standard Trick Room setups such as Cresselia, Musharna, and Bronzong, form good synergy with Rhydon, as their abilities allow them to avoid Earthquake. Gastrodon pairs well with Rhydon, as it won't have to worry anymore about common Water-type moves except for Surf and Muddy Water. Tyranitar and Hippowdon pair great with Rhydon, setting up a Sandstorm and boosting its Special Defense, making it even bulkier. Gyarados and other Flying-types pair fantastically with Rhydon, as its ability Lightningrod absorbs all Electric attacks that would usually give them trouble.

[Other Options]

Thankfully, Rhydon has a very wide movepool. Fire, Ice, and ThunderPunch provide decent coverage, and can hit some Pokemon better than its STABs will. Stone Edge is a less-accurate alternative to Rock Slide, but is powerful enough to be considered. Rock Blast can hit through Substitute, but is rather unreliable, as it only has a rare chance to hit five times in a row. Hammer Arm is interesting as it makes Rhydon faster in Trick Room, making it a considerable option. However, 90% accuracy can be unappealing at times for a 100 BP move. Crunch hits common Ghost-types such as Chandelure and Jellicent well, but Megahorn is the more powerful and more reliable option to hit Psychic-types. Superpower is very powerful, but decreases Attack and Defense after one use, which are Rhydon's best perks. Due to its bulk, Rhydon is one of the rare Pokemon who can set up Sandstorm for its team successfully, in case Politoed or Ninetales have been sent in, or the team lacks Tyranitar or Hippowdon.

[Checks and Counters]
Despite its mammoth defenses, Water and Grass-type moves still pose a huge threat to Rhydon, putting a huge dent in its HP. Like many of its Rock and Ground-type relatives, Rhydon has miserable Special Defense, so any super-effective special attack is harmful. Pokemon with Will-o-Wisp such as Sableye and Dusclops can quickly shut down Rhydon with a burn, and Rhydon has no real way to hit them back hard without Crunch. Hitmontop, Gyarados, and other common Pokemon with Intimidate can reduce Rhydon's firepower first turn, so it is advised to keep it away from the lead slot. Dual Steel-types such as Scizor and Ferrothorn take little from any attack besides the rare Fire Punch, and hit back hard with Bullet Punch or Power Whip.

I'd change the EV spread from 4 Def to 4 Sp.Def, since Rhydon isn't exactly hurting in the Defense department, and it's most vulnerable to special attacks. Also the Speed IV should be set to 0, since Rhydon is meant to operate in Trick Room.

I'm not sold on Drill Run over Earthquake. It's only 5 BP more than Earthquake against a single target (factoring in doubles damage penalty), and 5% less accurate. It is also more susceptible to Protect than Earthquake (since an opponent would have to double Protect to guarantee no damage). True, your partner needs a means to avoid Earthquake as well, but good teambuilding makes this a non-issue.

An EV spread of 60 HP / 244 Atk / 204 SpD might be better for Rhydon. It makes Rhydon considerably better at taking Special based attacks, without losing too much on Physical Defense. Metagross Meteor Mash is a 2HKO, and Garchomp multitarget Earthquake is a 3HKO, regardless of if you have 0 or 252 HP EVs. With 60 HP, you can take a Gem Close Combat from Hitmontop guaranteed. With 60 / 204, you can take a Gem Draco Meteor from Latios guaranteed.